WO1988003941A1

WO1988003941A1 - Cathodically separable, water dilutable binding agents, water dilutable coating compounds and process for producing said agents

Info

Publication number: WO1988003941A1
Application number: PCT/EP1987/000713
Authority: WO
Inventors: Michael Geist; Klaus Cibura; Helmut Fobbe; Günther OTT
Original assignee: Basf Lacke + Farben Aktiengesellschaft
Priority date: 1986-11-18
Filing date: 1987-11-16
Publication date: 1988-06-02
Also published as: EP0333759A1; EP0273170A1; ES2026170T3; US5086091A; BR8707884A; EP0273170B1; DE3639488A1; JPH01502911A; CA1305279C; DE3773630D1; ATE68198T1; JPH06102763B2

Abstract

Cathodically separable, water dilutable binding agents containing primary amino groups, neutralized by acids and introduced by means of ketimine groups. The binding agents are characterized by the fact that they are produced by reaction between (A) a synthetic resin containing epoxide groups and (B) at least one compound which, besides a mercapto group reacting with epoxide groups, has at least one ketimine group, and possibly (C) further modifying compounds, such as monocarboxylic acids and/or further primary and/or secondary amines, and that they are then neutralized with an acid.

Description

Cathodic water-thinnable binders, water-thinnable coating compositions and processes for the production of cathodic water-thinnable binders

The invention relates to cathodically separable water-thinnable binders which contain primary amino groups neutralized with acids and introduced via ketimine groups.

Cathodically depositable water-dilutable binders are required for the production of electrocoating materials for cationic electrocoating. Cationic electrodeposition coating is a coating method which is frequently used especially for priming, in which synthetic resins carrying water-thinnable cationic groups are applied to electrically conductive bodies with the aid of direct current.

It has been found that the presence of primary amino groups in the binder molecules has a positive influence on the quality of the coatings obtained.

For the introduction of primary amino groups into the binder molecules, it has been proposed to implement epoxy group-containing synthetic resins with (poly) ketimines which contain hydroxyl groups or secondary amino groups and then to release the primary amino groups hydrolytically (cf. US Pat. No. 3,947,339, US Pat. PS-4,017,438, US-PS-4,104,147 and US-PS-4,148,772). The introduction of primary amino groups via ketimine derivatives containing hydroxyl or secondary amino groups has the disadvantage, among other things, that these ketimine derivatives react with the epoxy groups so slowly that disruptive side reactions can occur and unreacted ketimine derivatives remain in the reaction mixture. These unreacted ketimine derivatives are hydrolyzed in the aqueous phase to give low molecular weight amines which have a negative effect on the properties of the electrodeposited and baked coatings.

The object of the present invention is to provide improved binders of the type mentioned at the outset.

This object is achieved by binders which have been produced by reacting

(A) with a resin containing epoxy groups

(B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketrmine group and optionally

(C) other modifying compounds such as monocarboxylic acids and / or further primary and / or secondary amines and then neutralized with an acid. ^"

All epoxy group-containing synthetic resins suitable as starting materials for the production of cathodically separable, water-dilutable binders can be used as component (A) (cf., for example, US Pat. No. 3,947,399, US Pat. No. 4,017,438, US Pat. No. 4,104,147, US -PS-4,148,772 and EP 4090).

Modified polyglycidyl ethers of polyphenols, polyglycidyl esters, epoxide-containing polyacrylates and epoxidized polybutadiene may be mentioned as examples.

Polyglycidyl ethers prepared from polyphenols, preferably bisphenol A, and epihalohydrins are preferably used as component (A). 1 The well-known modified polyglycidyl ethers of polyphenols ^* , preferably bisphenol A, are particularly preferably used. Modified polyglycidyl ethers of ^" polyphenols, preferably bisphenol, used with particular preference

5 A, are the polyglycidyl ethers of polyphenols modified by reaction with at least one compound which contains one or more, preferably two, hydroxyl groups per molecule bound to aromatic and / or (cyclo) aliphatic molecule fragments (cf., for example, German patent applications ₁₀ fertilizer P 36 18 157.9).

Compounds (B) used are compounds which, in addition to a mercapto group which is reactive towards epoxide groups, also have at least one ketimine group. 5 In addition to the mercapto and ketimine groups, the compounds can also contain further functional groups if these groups do not interfere with the synthesis of the binder.

As component (B), preference is given to compounds of the general formula ²⁰ HS-R ¹ - (N = CR ² R ³ ) _n (I), in which R is an organic group, preferably an alkylene group, R 2 and R3 are organic Groups, preferably alkyl groups with 1 to 4 carbon atoms, where R 2 and R3

25 together can also form a cycloaliphatic ring, and n stands for an integer ___. 1, is used. This

Compounds can by ketiminization of mercapto compounds of the general formula HS-R 1- (NH ₂ ) (R1 stands for an organic group, preferably an alkylene group, n

30 for an integer _ 1) with ketones of the general formula (R2 and R3 stand for organic groups, preferably alkyl groups with 1 to 4 carbon atoms, where R 2 and R3 together can also form a cycloaliphatic ring) can be easily prepared . He (B) components according to the invention

« _E can, for example, by reacting 2-mercaptoethylamine with

Acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,

Cyclopentanone or acetophenone can be produced. Methyl isobutyl ketone is preferably used. Compounds of the general formula are also preferred

HS-R ⁴ -CO-NE_ ⁵ -R ⁶ -N = CR ⁷ R ⁸ (II) (R stands for an organic one

5 group, preferably an alkylene group, R for an organic group, preferably an alkyl group, or for

-R -N = CR R, R for an organic group, preferably for an alkylene group and R 7 and R8 for organic groups, preferably alkyl groups with 1 to 4 carbon atoms, where R 7 and R8 together can also form a cycloaliphatic ring) used as component (B).

Connections of this kind can e.g. by reacting mercaptocarboxylic acids or mercaptocarboxylic acid esters with the corresponding ketines in the following reaction

, 4 8 equations are prepared (the radicals R to R have the same meaning as described above):

HS-R ⁴ -C00H + HNR ⁵ -R ⁶ -N = CR ⁷ R ⁸ → »(II) + ■ H ₂ 0

HS-R ⁴ -C00R ⁹ + HNR ⁵ -R ⁶ -N = CR ⁷ R ⁸ - (II) + HÖR ⁹ q R - represents an organic radical, preferably one

Alkyl radical with 1 to 4 carbon atoms.

The ketimines listed in the above reaction equations can be easily prepared by reacting the corresponding primary-secondary polyamines with appropriate ketones using well known methods. Examples of suitable primary-secondary polyamines are diethylenetriamine, dipropylenetriamine, dihexylenetriamine and hydroxyethylaminoethylamine.

Components (A) and (B) can either be reacted in such proportions that the reaction product no longer contains epoxy groups or that the reaction product still contains free epoxy groups which, depending on the desired product properties, can then be used for further modification reactions, such as, for example Reaction with monocarboxylic acids such as fatty acids or versatic acid and / or primary and / or secondary amines such as methylethanolamine or dicocosamine can be used. Self-evident The hydroxyl groups present in the reaction product can also be used for further modification reactions.

The binders according to the invention can be converted into self-crosslinking systems by further generally known methods and / or together with crosslinkers such as e.g. blocked polyisocyanates, phenolic resins, melamine resins or compounds with activated ester bonds can be used as externally cross-linking systems.

A self-networking system can e.g. are obtained by reacting the binder with a partially blocked polyisocyanate, which on average has one free isocyanate group per molecule and whose blocked isocyanate groups are only unblocked at elevated temperatures.

Finally, the binder obtained is dispersed in water with the addition of water-soluble acids (e.g. formic acid, lactic acid, propionic acid ...) and with hydrolysis of the ketimine groups and further processed to an aqueous electrocoat material by well-known methods.

The invention also relates to a process for the preparation of cathodically depositable water-dilutable binders which contain primary amino groups neutralized with acids and introduced via ketimine groups.

This method is _{characterized.} that (A) an epoxy group-containing synthetic resin with (B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketimine group and optionally also with (C) further modifying compounds, such as, for example, monocarboxylic acids and / or implemented further primary and / or secondary amines and the reaction product obtained is neutralized with an acid. The reaction of the epoxy resin with component (B) is preferably carried out at temperatures between 50 and 180 ° C. and can be catalyzed, for example, by adding tin octoate or ethyl triphenylphosphonium iodide. The reaction conditions should be chosen so that the blocked primary amino groups are only released when there are no longer any possibilities for the formation of higher molecular weight products.

The invention also relates to water-dilutable coating compositions for the production of preferably cathodically deposited thermosetting coatings, the binders of which at least partially consist of binders which contain primary amino groups neutralized with acids introduced via ketimine groups and which are characterized in that the primary amino groups containing binders have been prepared by reacting

(A) with a resin containing epoxy groups

(B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketimine group and, if appropriate

(C) other modifying compounds, e.g. Monocarboxylic acids and / or other primary and / or secondary amines and then neutralized with an acid.

In addition to the binder, the coating compositions according to the invention can also contain other conventional additives, such as e.g. Containing crosslinking agents, coalescing solvents, pigments, surface-active agents, crosslinking catalysts, antioxidants, fillers, anti-foaming agents, etc.

The water-dilutable coating compositions prepared with the aid of the binders according to the invention are particularly suitable for the cationic electrocoating process; but they can also be used in conventional coating processes. For example, optionally pretreated metals such as iron, steel, copper, zinc, brass, magnesium, tin, nickel, chromium can be used as coating substrates and aluminum, but also impregnated paper and other electrically conductive substrates can be used.

The advantages achieved with the invention consist in particular in the fact that the coating compositions produced from the binders according to the invention have a - compared to the prior art - a lower proportion of low molecular weight amines, which has a positive effect on the properties of the electrodeposited and baked coatings affects.

The invention is explained in more detail in the following examples. All information on parts and percentages are given by weight, unless expressly stated otherwise.

Example 1 - Preparation of a mercaptoalkyl ketimine

In a suitable reaction apparatus consisting of a reaction vessel, a stirring device and a water separator, 309 parts of dry diethylenetriamine are mixed in under an inert gas

400 parts of methyl isobutyl ketone dissolved. The reaction mixture is slowly heated to 145 ° C., 103 g of water collecting in the separator under reflux within 4 h. The resulting ketimine solution is then mixed with 325 parts of 3-mercaptopropionic acid at room temperature. Under normal pressure at 130 to 160 C 51 g

Water (94.4% of theory) was removed and the mercaptoalkyl ketamine solution was dissolved to 80% with methyl isobutyl ketone. Amine equivalent weight: 221 g / mol amine.

Example 2 - Representation of a crosslinker I

According to DE-OS 27 01 002, example 1, a blocked isocyanate crosslinker is prepared by slowly adding 218 parts of 2-ethylhexanol with stirring in a nitrogen atmosphere to 291 parts of an 80/20 isomer mixture of 2.4- / 2.5-

Toluene diisocyanate are added, the reaction temperature being kept below 38 ° C. by external cooling. The mixture is kept at 38 ° C. for a further half hour and then heated to 60 ° C., after which 75 parts of trimethylolpropane and then 0.08 part of dibutyltin dilaurate are added as a catalyst. After an exothermic reaction at the beginning, the batch is held at 121 ° C. for 1.5 hours until essentially all of the isocyanate groups have been consumed, which can be seen from the infrared spectrum. The mixture is then diluted with 249 parts of ethylene glycol monoethyl ether.

Example 3 - Representation of a crosslinker II

According to EP 57 389, example 1, a polyester crosslinker is produced. 109 parts of pentaerythritol are mixed with 474 parts of phthalic anhydride in a reaction vessel with a reflux condenser, stirrer, internal thermometer and gas inlet and heated to 140 ° C under nitrogen. The reaction is then exothermic and is kept at 160 ° C. by cooling. With an acid number of 305, the mixture is cooled and 300 parts of methyl isobutyl ketone are added. 231 parts of butylene oxide are slowly added dropwise at 90 ° C. and the batch is kept at the temperature until the acid number has dropped to zero.

Example 4 - Preparation of a dispersion I.

A reactor equipped with a heater, stirrer, cooler, thermometer and nitrogen inlet is charged with 837 parts of a bisphenol A epoxy resin with an epoxy equivalent weight of 188, 72 parts xylene, 254 parts bisphenol A and 3 parts dimethyl charged with thylbenzylamine. The temperature is raised to 130 ° C. and the reaction is carried out until an epoxy equivalent weight of 480 is reached. Then 300 parts of a commercially available polycaprolactone diol with a molecular weight of 535 and a further 3 parts of dimethylbenzylamine are added. The reaction is continued at 130 ° C. until the reaction mixture has an epoxy equivalent weight of 1200. Then 1200 parts of the previously described crosslinker II are added. The reaction temperature is reduced to 99 C by external cooling. 300 parts of the mercaptoalkyl ketimine described in Example 1 and 66 parts of N-methylethanolamine are metered in, the reaction temperature being kept below 110 ° C. by cooling. The reaction mixture is then diluted with 137 parts of hexyl monoglycol ether, cooled to 90 ° C. and discharged. The result is a clear resin solution.

In the meantime, a dispersion bath is prepared from 1485 parts of deionized water, 26 parts of glacial acetic acid and 2 parts of a commercially available defoamer, into which 2700 g of the resin solution described above are introduced with stirring. The dispersion mixture is allowed to stir for two hours, then a further 1825 parts of deionized water are added. The result is a low-viscosity dispersion with an experimentally determined solids content of 36.0%.

Example 5 - Preparation of a dispersion II

In a suitable reaction apparatus, 2000 parts of a commercially available bisphenol-A epoxy resin (epoxy equivalent weight 500), 116 parts xylene, 262 parts dodecylphenol and 314 parts dimenthylbenzylamine are reacted at 130 ° C. until an epoxide equivalent weight of 1100 is reached. Thereafter, 270 parts of xylene, 145 parts of hexylglycol and 160 parts of diethanolamine are added at 110 ° C., after a further 15 minutes 100 parts of the mercaptoalkylketimine described in Example 1 and 200 parts of butylglycol and 350 parts of isobutanol. The contents of the reactor are allowed to yaw for 60 minutes and then cooled to 90 ° C. and the clear resin solution is discharged.

1120 parts of the warm resin solution are introduced into a dispersion bath composed of 752 parts of deionized water, 0 350 parts of the crosslinking agent II described in Example 3, 2 parts of a commercially available defoamer and 13 parts of glacial acetic acid. After stirring for two hours, a further 960 parts of deionized water are added. A low-viscosity dispersion with an experimentally determined solid of 36.8% is obtained.

Preparation of the electro-immersion baths and deposition of paint films

0 1675 parts of deionized water are placed in a suitable vessel and 25 parts of 10% acetic acid are added. 2279 parts of the binder dispersion and 775 parts of the pigment paste described in EP 102 501 B1 (example 7) are stirred into this solution and made up with 246 5 parts of deionized water. Before the depositions, the paint baths are aged for 3 days with stirring. The coating films are deposited at 300 V for 2 minutes on zinc-phosphated steel sheets, which are connected as cathodes. After the usual aftertreatment, the films are baked at 180 ° C. for 20 minutes.

Separation result

Bad I II

Layer thickness (um) 20 23 at voltage (V) 300 370

History * 1.0 1.5

Crater rating * 0.5 0.5

Cross cut * 0 0

Reverse impact (inch pounds) 80 80

L (bath) ** 1.11 1.06

* 0 = best value 5 = worst value

** Conductivity of the paint bath in 10 -9S.cm-1

Claims

- ~

Patent claims

Cathodically separable water-dilutable binders which contain primary amino groups neutralized with acids and introduced via ketimine groups, characterized in that they have been prepared by reacting

(A) with a resin containing epoxy groups

(B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketimine group and optionally

2. Water-dilutable coating compositions for the production of preferably cathodically deposited heat-curable coatings, the binders of which at least partially consist of binders which contain primary amino groups neutralized with acids introduced via ketimine groups, characterized in that the binders have been prepared by implementing

(A) an epoxy group-containing synthetic resin with (B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketimine group and optionally (C) further modifying compounds, such as, for example, monocarboxylic acids and / or further primary and / or secondary amines and then neutralized with an acid. -43-

1 3. Binder or coating compositions according to claims 1 or 2, characterized in that as component (A) one made from a polyphenol, preferably bisphenol A, and an Ξpihalohydrin

5 polyglycidyl ether, has been used.

4. Binder or coating compositions according to claim 3, characterized in that a modified polyglycidyl ether, preferably a, as component (A)

10 modified polyglycidyl ether has been used by reaction with at least one compound which contains one or more, preferably two, hydroxyl groups per molecule bound to aromatic and / or (cyclo) aliphatic molecular fragments.

15

5. Binder or coating compositions according to one of claims 1 to 4, characterized in that as component (B) compounds of the general formula

20 HS-R ¹ - (N = CR ² R ³ ) _n (I),

in which R is an organic group, preferably an alkylene group, R 2 and R3 are organic groups, preferably alkyl groups having 1 to 4 carbon atoms, R 2 and R3 together also being a cycloaliphatic ring

25 can form, and n stands for an integer ≥, 1, have been used.

6. Binder or coating compositions according to one of claims 1 to 5, characterized in that

30 as component (B) compounds of the general formula

HS-R ⁴ -C0-NR ⁵ -R ⁶ -N = CR ⁷ R ⁸ (II),

4 in the R for an organic group, preferably

³ O ⁵ K is an alkylene group, R5 is an organic group,

6 7 8 preferably an alkyl group, or for -R -N = CR R, g R for an organic group, preferably for an alkylene group and R 7 and R8 for organic groups, preferably alkyl groups having 1 to 4 carbon atoms, where R 7 and R8 together can also form a cycloaliphatic ring.

7. A process for the preparation of cathodically separable water-dilutable binders which contain primary amino groups introduced with acids neutralized via ketimine groups, characterized in that

(A) a synthetic resin containing epoxy groups

(B) at least one compound which, in addition to a mercapto group reactive towards epoxy groups, also has at least one ketimine group and 5 optionally also with

(C) other modifying compounds, such as monocarboxylic acids and / or further primary and / or secondary amines, are reacted and the reaction product obtained is neutralized with a _Q acid.

5

0

5